i 5 8 A E R O 
this fubjeft (fays he) until 1 read the work of Mr. Me- 
therie; who afferts, that nitrous air contains no proper 
nitrous.acid, but only one of the elements of it; the other 
being dephlogifticated air, Which had before been confi- 
dered by M. Lavoifier as the principle of all acidity. 
Among other obferyations in fupport of his affertion, Mr. 
Metherie has the following: — i. Nitrous air burnt toge¬ 
ther with inflammable air produces no nitrous acid. 2. 
Though nitrous air be obtained from a folution of mer¬ 
cury* in the nitrous acid, a!mo'ft all the acid is found in 
the folution. 3. Nitrous air abforbed by marine acid does 
not make aqua regia. 4. He is of opinion, that a finall 
portion of the nitrous acid, being decompofed, furnifhes 
a pure air, fo altered, that, uniting with inflammable air, 
it changes it into nitrous air. To afcertain the matter 
more fully, the doctor proceeded to try various experi¬ 
ments on the decompofition of nitrous air, particularly 
that of burning Homberg’s pyrophorus ; but without flic- 
cefs, or obtaining the fmalleft particle of nitrous acid.— 
His epnelufions from the whole are thefe : Water feems to 
be a neceffary ingredient in nitrous as well as inflammable 
air ; at lead, without a quantity of water, nitrous air can¬ 
not be formed. For example, copper will be dilfolved in 
ftrong nitrous acid without producing any nitrous air, juft 
as iron may be dilfolved in concentrated vitriolic acid with¬ 
out producing inflammable air. 
“ That nothing is neceffary to the formation of nitrous 
air befides phlogifticated nitrous acid and water, is evident 
from the production of it by the impregnation of pure water 
with phlogifticated nitrous vapour formed by the rapid fo¬ 
lution of bifmuth. Nitrous air is alfo produced by pour¬ 
ing a highly-coloured or phlogifticated nitrous acid into 
pure water, in which no metal or earthy matter is any 
way concerned. 
“ I have formerly obferved, how readily nitrous air is 
diminifhed by taking the electric fpark in it. This expe¬ 
riment I have frequently repeated, in order more particu¬ 
larly to afcertain the quantity and quality of the reliduum. 
In one experiment, the eledtric fpark was taken in a quan¬ 
tity of nitrous air till it could be no more diminifhed, when 
it was reduced in bulk in the proportion of ten and a half 
to twenty-four. Letting it ftand all night upon the mer¬ 
cury, it was increafed in the proportion of eleven and a 
quarter to twenty-four^ feemingly by the acid uniting to 
the mercury and generating more nitrous air, (ince it had 
that fmell. No water appeared after the procefs; and the 
water admitted to it acquired no acid tafte, but an aftrin- 
gent one like that of water impregnated with nitrous air. 
There was a white powder formed, as in the former ex¬ 
periments. To try if it were poflible to make water im¬ 
bibe the acid from the nitrous air, the electric fpark was 
taken in it, with a fmall quantity of water over the mer¬ 
cury. But even this water did not acquire any acid tafte, 
but only an aftringent one.” 
The doctor concludes this fubjeft with a conjecture, 
that the phlogiftion, and neither the heat nor light of the 
eleftric fpark, contributes to the decompofition of the 
nitrous air. 
Of Dephlogijlicatcd Nitrons Air. 
This fpecies of air differs from common nitrous air in 
being able to fupport flame, though it ftill continues fatal 
to animal life. Common nitrous air may be converted in¬ 
to the dephlogifticated. When zinc is dilfolved in nitrous 
acid, if the air be taken at different times, that which 
comes about the latter end of the procefs will be of this 
kind, and not only fupport the burning of a candle, but 
caufe the flame to enlarge greatly by the addition of a 
weaker and blueifti flame round the former ; and this with 
a crackling noife, as if the candie were burning in de¬ 
phlogifticated air. It may alfo be obtained in procuring 
nitrous air from iron, though this metal is uncertain: 
but tin yields a confiderable quantity of it. By expofmg 
iron to nitrous air, it may be fo far dephlogifticated as to 
LOGY. 
admit a candle to burn in it, but the experiments made 1 
with that metal have proved remarkably uncertain and 
inconclufive. 
In deferibing the component parts of this kind of air,, 
Dr. Prieftlev obferves, that water is abfolutely neceffary to> 
its compofition, or rather to the decompofition of the com¬ 
mon nitrous air by ifton. He had decompofed it before, ei¬ 
ther by previoufly filling the veffels that were to contain the 
nitrous air with water or with mercury; though it had al¬ 
ways required a much longer time when the latter was. 
made ufe of. The reafon of its being formed at all m 
this laft way, was a fmall quantity of moifture adhering 
to the infide of the velfel containing the mercury. 
To try the influence of water, he put a number of ve¬ 
ry clean fmall needles into a vial, and, filling it up with 
mercury, introduced the nitrous air: but it continued fix 
or eight months without alteration. Introducing a few 
drops of water, a diminution of about one-third of the 
air took place, and the remainder appeared to be phlo¬ 
gifticated. In another experiment with iron-(havings, 
one-half was abforbed, and the remainder fupported the 
flame of a candle better than common air, though amoufe 
died in it; and yet this air had continued feveral months- 
in the fame (late with regard to its quantity and quality. 
Though this kind of air is produced by the contact of 
iron and nitrous air, the doftor had never been able to- 
afcertain the quantity of nitrous air which a given quan¬ 
tity of iron can decompofe ; and, though iron foon becomes 
fo much affected by this procefs that it crumbles into 
powder, it ftill feems equally capable of decompofing a 
frefli quantity. Having made a comparative experiment, 
by putting together one quantity of nitrous air with frefti 
iron and another with ruft, lie found that in both the air 
was diminiflied to about one-third, and a candle burned 
in both equally well; but neither of them had the pro¬ 
perties of .frefli nitrous air in any degree. 
As the procefs for obtaining dephlogifticated nitrous 
air by means of iron is very tedious, the doftor endea¬ 
voured to find another which might be attended witli le-fs, 
inconvenience. This he accompliftied by diffoiving turn¬ 
ings of iron in a dilute folution of copper in nitrous acid 
(the fame that remains after the production of nitrous air), 
mixing it again with an equal quantity of water. With¬ 
out this precaution, he tells us, that, though the iron will 
at firft be afted upon very (lowly, yet the mixture will at 
length grow fo hot as actually to boil, and the procefs 
will be exceedingly troublefome : however, it will be ne- 
ceffary, previous to any attempt to diffolve the iron, to 
heat the folution of copper, in order to expel all the ni¬ 
trous air and fuperfluous nitrous acid. Without this pre¬ 
caution a quantity of common nitrous air will be produced. 
Water abforbs dephlogifticated nitrous air ahnoft as 
readily as fixed air; taking up about one-half its bulk of 
air. After being thus faturated, the whole quantity of 
dephlogifticated nitrous air may be expelled pure by heat. 
It refembles fixed air alfo in this farther property, that all 
the air which has been actually incorporated with the wa¬ 
ter will not be imbibed by water again. But the propor¬ 
tion of this part is three or four times greater than the 
correfponding part of fixed air; and is alfo much more 
phlogifticated. Water very foon parts with it on being 
expofed to the atmofphere. Neither acid nor alkali can 
be difeovered in it. Its fpecific gravity is lefs than that 
of common air. On heating red precipitate in it, pure 
dephlogifticated air was produced without affedling, or 
being affected by, the nitrous air. Malleable iron occa- 
fiOned the quantity of it to be enlarged, and the whole 
phlogifticated, without any mixture of fixed air. By heat¬ 
ing bits of clean crucibles or retorts in this kind of air,, it 
feemed to approach in quality to common atmofpherical 
air. By the eledlric fpark it became immifcible with wa¬ 
ter, and was brought to the ftandard of 1-45; fo that 
there feemed to be no. doubt of its being refpirable. Yet 
this kind of air, though a candle burns fo well in it,- will 
3 nol 
